904 PALEONTOLOGY OF NEW- YORK. 



to the front. The plications on the sides are more or less abruptly 

 curved to the margins of the shell. The shell, when preserved, is marked 

 by fine close concentric striae : the specimens are usually casts. 



I have referred to this species some gibbous forms with moderately elevated 

 mesial folds, in which the plications are aubangular or rounded, and the entire 

 shell preserves a rotund form. The original of this species is the largest one that 

 has been observed, and is nearly an inch in length, with a somewhat greater breadth. 

 The more common forms are about three-fourths of au inch in diameter. 



This species presents many features in common with R. sappho of the Hamilton 

 group ; and I am prepared to find, among larger collections, a gradation from 

 one to the other. 



Qtological formation and localitiea. This species has been fouud in the higher 

 beds of the Chemung group ; in Chautauque countj^, New- York ; at Meadville, and 

 in some loose masses of the group on Oil creek, Pennsylvania. 



Rlijuclionella (Stenocisiua) sappho, var. 



PLATE LV. 



Specimens from the ferruginous sandstone of Licking county, Ohio, 



present all the characteristic features of R. (S.) sappho of the Hamilton 



group. The specimens vary from about half an inch to three-fourths of 



an inch in length, with a somewhat greater hreadth. The plications vary 



from obtusely angular to rounded, and often show a distinct groove 



towards the margin of the shell. 



This form is common and even abundant in the ferruginous sandstones known 

 as the upper part of the Waverly sandstone series of Ohio, and it is introduced 

 for comparison with the Hamilton and Chemung forms of New- York. 



